1. Field of the Invention
The present invention relates to an optical waveguide with photoelectric conversion element suitable for use in optical touch panels and an optical touch panel.
2. Description of Related Art
FIG. 5 shows an optical waveguide 30 with photoelectric conversion element as an example of a conventional optical waveguide with photoelectric conversion element (see, for example, JP 2008-203431 A). The conventional optical waveguide 30 with photoelectric conversion element includes a plurality of cores 31 through which light propagates, an under-cladding layer 32 supporting the cores 31, an over-cladding layer 33 embedding the cores 31, and a photoelectric conversion element 34. The over-cladding layer 33 is equipped with a convex lens portion 33a whose cross-sectional shape is substantially a quarter of a circle.
FIG. 6 (a) is a schematic view of the conventional optical waveguide 30 with photoelectric conversion element when used as a light emitting-side optical waveguide. In this case, a light emitting element which converts electrical signals into optical signals is used as the photoelectric conversion element 34. Each of the cores 31 has an end 31a and the other end 31b, and the other end 31b of each of the cores 31 is optically coupled to a light emitting port of the photoelectric conversion element 34. Light (indicated by a dotted line) emitted from the photoelectric conversion element 34 enters the cores 31, propagates through the cores 31, emerges from the ends 31a of the cores 31, and enters the over-cladding layer 33. The diverging light emerging from the ends 31a of the cores 31 is collimated by the convex lens portion 33a and outputted as parallel light 36.
FIG. 6 (b) is a schematic view of the conventional optical waveguide 30 with photoelectric conversion element when used as a light receiving-side optical waveguide. In this case, a light receiving element which converts optical signals into electrical signals is used as the photoelectric conversion element 34. Wide parallel light 37 received by the surface of the convex lens portion 33a of the optical waveguide 30 with photoelectric conversion element is concentrated by the convex lens portion 33a onto the ends 31a of the cores 31 in the over-cladding layer 33, enters the cores 31, propagates through the cores 31, enters the photoelectric conversion element 34 optically coupled to the ends 31b of the cores 31, and is then converted into electrical signals. Here, the term “optically coupled” means that the photoelectric conversion element 34 and the ends 31b of the cores 31 are coupled to each other so that light can efficiently transmit from the photoelectric conversion element 34 to the cores 31 or from the cores 31 to the photoelectric conversion element 34.
Such an optical waveguide 30 with photoelectric conversion element is suitable for use in optical touch panels. FIG. 7 (a) is a schematic view of the conventional optical waveguide 30 with photoelectric conversion element when used as a light emitting-side optical waveguide in an optical touch panel 40. FIG. 7 (b) is a schematic view of the conventional optical waveguide 30 with photoelectric conversion element when used as a light receiving-side optical waveguide in the optical touch panel 40. As shown in FIGS. 7 (a) and 7 (b), in the optical touch panel 40 using the conventional optical waveguides 30 with photoelectric conversion element, the photoelectric conversion element 34 of each of the optical waveguides 30 with photoelectric conversion element and its associated circuit (not shown) are arranged on the face side of a display panel 43. This makes it difficult to reduce the size of a frame 42 of the optical touch panel 40 and the difference in level on the surface of the frame 42 and its vicinity. It is to be noted that the surface of the display panel 43 serves as a coordinate input region 41.
As described above, in the optical touch panel 40 using the conventional optical waveguides 30 with photoelectric conversion element, the photoelectric conversion element 34 of each of the optical waveguides 30 with photoelectric conversion element and its associated circuit are arranged on the face side of the display panel 43. This makes it difficult to reduce the size of the frame 42 of the optical touch panel 40 and the difference in level on the surface of the frame 42 and its vicinity.